Loki

His human form is a teenage viking wearing goth clothes and a demonic skull helmet. He plots on overthrowing Odin by framing Earth for a crime againnst the gods, which will eventually lead to a war. Not much is known about him at the time, although he is a charismatic character, he is the father of Hell who befriends Hiccup, Astrid, Snoutlout and Ruffnut and Tuffnut. In the trailer he is seen wielding a giant scythe, leading an army of monstrous deathless warriors, taunting the main characters, giving a speech to his army, confronting an angry Odin and fighting Hiccup and Toothless in a seemingly climatic battle.

Quotes

And so it begins.

I AM A GOD.

(from trailer) My father turned his back on me, my children were taken from me, I am Lord of the underworld and I will lead you to victory.

Trivia

In the trailer Astrid mentions she has seen "dragons going wild..... animals suddenly dying...... babies crying before they are born, and skeleton warriors rising up." This leads some to speculate Loki's doings but it contradicts this because the army Loki was leading was demonic, not undead.

In the trailer some parts feature him being voiced by Marlion Manson or Kid Rock, while other parts of the trailer have him voiced by Zac Efron, Robert Patterson or Justin Bieber.